1. Field of the Invention
The present invention relates generally to mounting brackets for securing a steering column assembly to an automotive chassis. More particularly, the present invention relates to a mounting bracket for rotatably securing the lower jacket of a telescopic steering column assembly to a vehicle chassis.
2. Description of the Related Art
One conventional type of steering column assembly comprises two shaft sections supported in a two-piece telescopic jacket assembly wherein an upper jacket is telescopically collapsible relative to a lower jacket. This telescoping may occur upon a front end impact of the vehicle. Typically, a bracket rigidly mounts each of the jackets to the vehicle chassis. Examples of such brackets are disclosed in U.S. Pat. Nos. 1,435,990; 3,492,888; 4,086,825; 4,274,299; 4,400,990; 4,616,522; and 4,867,003. Each of these patents disclose the use of mounting brackets which mount the steering column assembly to the vehicle chassis.
It has been proposed to mount an energy absorbing element coaxially with and between the two jackets such that the energy absorbing element deforms under impact loads generated during a front end collision. In this manner, the steering column collapses at a controlled rate so that the kinetic energy of impact is absorbed in a gradual movement of the column. One such type of energy absorbing element is shown in U.S. Pat. No. 3,788,148 wherein a plurality of deformer balls are disposed in preformed recesses between the telescoping jackets. During an impact, the balls remain in their preformed recesses until a predetermined load is exceeded, whereafter the balls engage the jacket walls in an interfering relationship to absorb energy. The upper and lower jackets must remain aligned during the impact so that the balls remain in the preformed paths during the loading to provide the controlled collapse of the steering column. Also, the jackets must remain aligned to prevent binding of the jackets as the jackets telescope with respect to one another. However, the prior art mounting brackets often do not maintain the jacket alignment under the axial load.
However, if the two jackets become misaligned with respect to one another as a result of angular misalignment of the column mounting points during assembly or due to twisting of the mounting brackets during structural deformation during the collision, the energy absorbing elements are forced out of their predetermined relationships with the jackets and controlled collapse of the steering column is impaired. Therefore, it would be advantageous to provide a means of eliminating the torsional misalignment of the jackets with respect to one another to ensure a properly controlled collapse of the steering column.
It is an object of the present invention to provide a mounting bracket which overcomes the disadvantages discussed above due to rigidly mounting the jackets to the vehicle and the misalignment of the upper and lower jackets with respect to one another under the imposition of an axial load upon the steering column.
It is a further object of the present invention to eliminate the load sensitivity of the steering column to misalignment of the energy absorbing element as well as mounting point misalignment and torsional twist of the assembly during an axial loading upon the steering column by permitting the lower jacket to rotate relative to the mounting bracket of the steering column assembly.
It is a feature of the invention to provide a mounting bracket for rotatably mounting the lower jacket to the vehicle which allows the lower jacket as well as the steering column assembly to rotate with respect to the mounting bracket upon imposition of an axial load upon the steering column to minimize torsional loads placed upon the column assembly by preventing relative twist between the jackets.